Beyond Traditional NDT: How Advanced Inspection Delivered Critical Insight into a Wisconsin Forcemain

For more than 140 years, the City of Marshfield, Wisconsin has maintained a strong commitment to environmental protection and reliable wastewater service. Serving nearly 20,000 residents, the city operates over 138 miles of sanitary sewer infrastructure supported by lift stations and forcemains that transport wastewater to treatment facilities. Like many utilities, Marshfield historically focused inspection and maintenance efforts on gravity sewers, while pressurized forcemains remained more difficult to assess—until a major leak highlighted the need for deeper pipeline intelligence.

A Leak Reveals Hidden Risks

In November 2023, plant operators noticed the wastewater treatment facility was receiving approximately one million gallons per day less flow than normal. Investigation revealed a leak in a 20-inch, two-mile cement-lined ductile iron forcemain connected to the Northeast Lift Station. The leak surfaced through a corroded stormwater culvert and was ultimately traced to severe external corrosion that created a four-inch hole in the pipe. While the damaged section was repaired, city officials recognized the event could signal broader system deterioration.

With lift station upgrades already in design, Marshfield incorporated a comprehensive forcemain inspection into the project. After evaluating qualified contractors, the city selected CPM Pipelines to conduct a full condition assessment using advanced in-line non-destructive testing (NDT).

Advanced NDT Provides Comprehensive Condition Intelligence

The inspection was completed in August 2025 using an intelligent pipeline inspection gauge equipped with ultrasonic sensors, inertial measurement technology, and acoustic monitoring. This sophisticated inspection allowed engineers to evaluate wall thickness, joint alignment, liner integrity, and external corrosion—without excavation or service disruption.

The results revealed several critical findings. While pipeline alignment generally matched as-built drawings, numerous structural concerns were identified. Nine pipe joints exceeded acceptable deflection thresholds, and two joints displayed excessive gap widths requiring ongoing monitoring. More importantly, ultrasonic measurements showed that corrosion damage was clustered primarily in the developed residential section of the pipeline, while segments routed through undeveloped land remained in significantly better condition.

Although average wall thickness remained within acceptable limits, localized external corrosion created areas of serious structural loss. Inspection data also identified more than 4,300 instances of liner delamination and widespread deterioration along the pipe invert, likely caused by calcium leaching or sediment abrasion. Encouragingly, acoustic analysis detected no active leaks, and only minor early-stage sulfate attack was observed.

Turning Data into Strategic Asset Management

Beyond identifying defects, the inspection delivered valuable operational insight. High-precision mapping confirmed pipeline location within six feet of recorded GIS data, improving future planning accuracy. The inspection also demonstrated a correlation between roadway de-icing salt usage and increased corrosion in pipe segments located beneath streets—providing the city with actionable information to support broader infrastructure protection strategies.

Perhaps most importantly, the inspection confirmed that deterioration was not uniform along the pipeline. Instead, damage was concentrated in specific segments, allowing Marshfield to consider targeted rehabilitation options such as localized lining or cathodic protection. This data-driven approach enables utilities to maximize infrastructure lifespan while minimizing capital and construction costs.

The Future of Forcemain Asset Management

Marshfield’s experience demonstrates how advanced NDT technologies are transforming underground infrastructure management. By delivering precise, repeatable condition data, modern inspection tools provide utilities with far more than defect identification—they provide the knowledge required to make informed operational, financial, and long-term asset management decisions.

As utilities nationwide face aging infrastructure and increasing environmental responsibility, projects like this highlight the growing importance of proactive, technology-driven pipeline evaluation programs that reduce risk, extend service life, and protect public health.